marsadm: fix recursion depth of _get_common_ancestor()
marsadm: fix split brain detection
marsadm: fix warning
all: fix inconsistent terminology apply->replay

In most cases, "replay" was already used. So it is easier
to switch the rare "apply" wording to "replay" everywhere (hopefully).
light: fix fetch at primary side
infra: add flood protected syslogging
light: add per-resource emergency mode
light: add info symlinks
light: show connection info
copy: add timestamp of last advance
light: show new {fetch,sync} info
marsadm: path correction / systematic naming conventions
light: allow limiting the sync parallelism
marsadm: prefer 'fetch' over 'connect'
marsadm: implement new 'view' command
doc: update
Changelog (incomplete)